Identification and Partial Characterization of Viral Agent of Lettuce Big Vein in Tehran Province

Background and Aims: The causal agents of viral lettuce big vein disease are two viruse, Lettuce big vein associated virus (Varicosavirus) and Mirafiori lettuce virus (Ophiovirus). These viruses have coat proteins of similar size but have different morphologies and serologically unrelated.The purpose of this study was to distinguish and detect LBVaV and MiLV in lettuce fields in Tehran Province. Patients and Methods: A total 344 samples with mosaic and big vein, head stunt, leaf deformation and motteling symptoms were collected from lettuce fields in Tehran Province.Using DAS – ELISA and specific antiserum for MiLV (DSMZ, AS-0798) and RT-PCR for LBVaV. Positive samples in ELISA and RT-PCR were inoculated on index plants,including Chenopodium quinoa, Chenopodium amaranticolor, Lactuca sativa and Nicotiana occidentalis p1. Results: The results of ELISA and RT-PCR about MiLV showed that, virus is transmitted on C.quinoa and produced chlorotic local lesion but about LBVaV, RT-PCR showed that C.quinoa and C.amaranticolor were infected and the virus caused chlorotic local lesion. Extraction of total RNA with three methods using RNAWIZ buffer, Guanidium isothiosianat buffer and Qiagen kit showed that exteraction with RNeasy plant minikit (Qiagen company) is better for RT-PCR. RT-PCR with LBVaV and MiLV specific primer pairs (were designed with Navaro et al. 2004) were performed and the fragment length were amplified for LBVaV and MiLV respectively 296bp and 469bp. The sequence nucleotides of CP of LBVaV was determined and had high similarity with other isolates in gene bank. Conclusion: This is the first report of occurrence of these viral diseases in lettuce in Iran (Tehran Province).